Employee Benefits - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
401(k) Retirement Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Company's share of discretionary matching contributions	$ 0.8	$ 0.8	$ 1.0

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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